1. Field of the Invention
The present invention relates to a backlight with a planar spread by which a display panel or the like is illuminated from behind.
The backlight of the present invention can be advantageously used with a device requiring a high luminance, such as a color liquid crystal TV or various office automation (OA) devices, but is not limited to such usages.
2. Description of the Related Art
A backlight which can provide a planar illumination is incorporated in an instrument panel of an automobile or airplane, etc., and recently the application of such a backlight has been widened to include a liquid crystal TV or a liquid crystal display.
As can be seen in FIG. 8, a conventional backlight usually has a transparent light guide plate 12 of acrylic resin or the like which is located between two cold-cathode tubes 11, so that light emitted from the cold-cathode tubes 11 is transmitted through the transparent light guide plate 12 and is totally reflected by a reflecting surface 13 which has a rough finished surface. Consequently, the reflected light is emitted from the light guide plate 12 and is made incident on a display panel 14 for display, such as a liquid crystal panel, through a diffusion plate 15 located in front of the light guide plate 12.
The conventional backlight as shown in FIG. 8 has the following drawbacks:
1 the light guide plate 12 is a solid flat plate and thus is heavy;
2 no emitted light scattered in different directions from the cold-cathode tubes 11 is effectively made incident on the light guide plate 12, and thus a satisfactory luminance cannot be obtained; and,
3 due to an irregular roughness of the reflecting surface 13, there is a tendency for the occurrence of an irregular luminance of the display surface of the backlight.
The primary object of the present invention is to provide a light and thin backlight having a high luminance and a uniform luminance distribution.